Okay my question is ? I just bought a 2005 s40 t5 I only had it for three weeks now I drove it four times. And now it acts like it doesn't want to pull losing power and a little shake not a bad shake .it feels like it's going to stop on me and now I won't drive it .it also has a check engine light on and it wasn't on for the first three weeks I had it but like I said I only drove it four times. The check engine light now blink on and off then comes back on and stay and after a minute or two it blink again. And I noticed when I put gas in my car the gas cap is broken do enyone know if my gas cap is the reason for my losing power. Please help .

 

No it is not. You need to at least have the codes read.

 

I think it will blink when the engine misfires. Not 100% sure on that though. As ES6T wrote, you need to have the trouble codes read. You can have Autozone or Advance (et al) read the codes for free. They do this because they want your business.

I too have a 2005 T5 S40 and it's been pretty much rock solid. The only time it acted as you describe was when the Fuel Pressure Sensor started to act up. My wife got something like a "reduced engine performance" message. It was intermittent though. I replaced the FPS and the problem never returned.